KR101069235B1 - Oled device having microcavity gamut subpixels - Google Patents

Abstract

The present invention produces an array of light emitting pixels, in which each pixel comprises organic layers comprising one or more light emitting layers for generating light and subpixels having spaced apart electrodes, here a color defining color gamut. Three or more gamut subpixels and one or more subpixels that generate light within the color gamut generated by the gamut subpixels), wherein one of the gamut subpixels The foregoing relates to an organic light emitting device having a reflector and a semi-transparent reflector which serve to form a microcavity.

Description

OLED DEVICE HAVING MICROCAVITY GAMUT SUBPIXELS

The present invention relates to microcavity organic electroluminescent (EL) devices.

Full color organic electroluminescent (EL) devices, also known as organic light emitting devices or OLEDs, have recently been demonstrated as a new type of flat panel display. In its simplest form, the organic EL device includes an anode for hole injection, a cathode for electron injection, and an organic EL medium that supports recombination of charges inserted between these electrodes to emit light. Examples of organic EL devices are disclosed in commonly assigned US Pat. No. 4,356,429. In order to construct useful pixelated display devices such as in televisions, computer monitors, cell phone displays or digital camera displays, the individual organic EL elements can be arranged as pixel arrays in a matrix pattern. To produce a multicolor display, the pixels can be further arranged in subpixels, each emitting a different color. The matrix of pixels can be electrically driven using either a simple passive matrix or an active matrix drive scheme. In the passive matrix, the organic EL layer is inserted between two sets of orthogonal electrodes, arranged in rows and columns. Examples of passive matrix driven organic EL devices are disclosed in commonly assigned US Pat. No. 5,276,380. In an active matrix arrangement, each pixel is driven by several circuit elements such as transistors, capacitors and signal lines. Examples of such active matrix organic EL devices are provided in US Pat. Nos. 5,550,066 (co-assigned), 6,281,634 and 6,456,013.

Full color OLED devices are also known in the art. A typical full color OLED device is built of pixels with three subpixels of red, green and blue. This arrangement is known as an RGB design. An example of an RGB design is disclosed in US Pat. No. 6,281,634. Full color organic electroluminescent (EL) devices have also recently been described as consisting of pixels having four subpixels of red, green, blue and white. This arrangement is known as an RGBW design. Examples of RGBW devices are disclosed in commonly assigned US Patent Publication No. 2002 / 0186214A1. RGBW devices use high efficiency white light emitting pixels to display a portion of the digital image content. This improves power consumption compared to RGB consisting of similar OLED materials. However, the red, green and blue subpixels do not improve the efficiency in this design. Thus, there is no power saving in displaying any portion of digital image content that is pure red, pure blue, or pure green, such as icons and toolbars commonly used in many personal digital assistants (PDAs), mobile phones or digital camera applications. . In addition, adding a fourth subpixel requires that all red, green, and blue subpixels be made small in order to match the total number of subpixels per unit area and to obtain the same device pixel resolution as the RGB devices being compared. . Thus, in order to display pure red, pure blue or pure green content at the same brightness, the current density per unit area of the associated red, green and blue subpixels must be increased. It is known that as current density increases, OLED devices degrade faster or become less efficient. In the case of RGBW displays, this results in pure red, pure green, or pure blue content, often appearing as icons and toolbars, causing image burn-ins faster than in equivalent RGB displays, and thus overall device Life is reduced.

Therefore, there is a need for an RGBW device with improved efficiency and lifetime of red, green and blue subpixels.

Summary of the Invention

It is an object of the present invention to use an OLED display device having a pixel with a mute subpixel and an intra-gamut subpixel that can substantially improve the efficiency of said mute subpixel.

This purpose is to (a) an array of luminescent pixels, in which each pixel comprises organic layers comprising one or more luminescent layers generating light and subpixels having spaced apart electrodes, here a color defining color gamut Three or more gamut subpixels that generate C and one or more subpixels that generate light within the color gamut generated by the gamut subpixels); (b) wherein at least one of said mute subpixels is achieved by an OLED device, including a reflector and a semi-transparent reflector, which act to form a microcavity.

By constructing a gamut subpixel with a microcavity structure, the present invention provides improved efficiency and lifetime. It is a further advantage that such a device can be built using an OLED organic layer common to all subpixels and does not require accurate patterning along the subpixels. Such a device has the further advantage that it can be deployed without the need of a color filter element, thereby reducing the cost.

1A-1D illustrate an RGBW pixel pattern layout that may be used in accordance with the present invention.

2 shows a cross sectional view of a pixel according to an embodiment of the invention.

3 shows a cross sectional view of a pixel according to another embodiment of the invention.

4 shows a cross sectional view of a pixel according to another embodiment of the invention.

Explanation of the sign

20: pixels

21a: the mute subpixel

21b: the mute subpixel

21c: mute subpixel

21d: Gamut-My Subpixels

22a: Non-microcavity gamut subpixel

22b: Microcavity Gamut Subpixel

22c: Microcavity Gamut Subpixel

22d: Gamut-My Subpixels

30a: light

30b: light

30c: light

30d: light

100: substrate

110: active matrix circuit

111: semiconductor active layer

112: gate dielectric

113: gate conductor

114: first insulating layer

115: power line

116: signal line

117: second insulating layer

120a: semi-transparent reflector

120b: semi-transparent reflector

120c: semi-transparent reflector

130: transparent electrode

130a: transparent electrode

130d: transparent electrode

140a: transparent cavity-spacer layer

140b: transparent cavity-spacer layer

150a: reflector

150b: reflector

150c: reflector

150d: reflector

160: inter-pixel dielectric

210: hole injection layer

212 hole transport layer

213: light emitting layer

214: electron transport layer

220: reflector

230: semi-transparent reflector

240: transparent electrode

310: color filter

RGBW displays are an example of a type of display that uses in-mute light emission to improve power consumption. Such display devices can display color images by using pixels having four or more different color subpixels. Three or more of the subpixels are gamut subpixels that emit different colors, which define the color gamut of the display. For example, the mute subpixels may emit light of either red, green or blue. Different colors can be created by illuminating two or more of the mute subpixels at different intensities. This new color is the gamut-in-color. Such display devices also have one or more additional subpixels that are intra-gamut sub-pixels, which emit in-mute color light, such as white. As used herein, the term "white" refers to any light emission that is perceived to be approximately white by the viewer. This intra-gamut subpixel is generally more effective than the gamut subpixel. 1 illustrates an example pixel arrangement for an RGBW device.

1A shows a stripe pattern arrangement of RGBW device pixels 20. Pixel 20 includes gamut subpixels 21a, 21b and 21c, and also intra-gamut pixels 21d. These subpixels may have, for example, red (R), green (G), blue (B) and white (W), respectively.

1B shows a quadrant pattern arrangement of RGBW device pixels 20. Pixel 20 includes gamut subpixels 21a, 21b and 21c, and also intra-gamut pixels 21d. These subpixels may have, for example, red (R), green (G), blue (B) and white (W), respectively.

1C shows another pattern arrangement of RGBW device pixels 20. Pixel 20 includes gamut subpixels 21a, 21b and 21c, and also intra-gamut pixels 21d. These subpixels may have, for example, red (R), green (G), blue (B) and white (W), respectively.

1D shows another pattern arrangement of RGBW device pixels 20. Pixel 20 includes gamut subpixels 21a, 21b and 21c, and also intra-gamut pixels 21d. These subpixels may have, for example, red (R), green (G), blue (B) and white (W), respectively.

Other patterns of RGBW can be applied to the present invention. In addition, a pattern with four or more subpixels may also be applied. In the above-mentioned example, the subpixels are shown to be arranged in a specific order, but in other embodiments, the subpixels may be arranged in a different order. In addition, although the subpixels are all presented to be the same size and shape, those skilled in the art will recognize that other embodiments may have subpixels having different sizes and shapes.

This type of display is more effective than conventional OLED displays because in-gamut subpixels tend to have higher efficiency compared to one or more of the gamut subpixels. Typically intra-gamut subpixels are more effective than all the gamut subpixels. Each subpixel can be fabricated using individual OLED materials designed to emit different color light. However, the preferred arrangement uses broadband or white light emitting OLED materials that are common to all pixels. The use of broadband or white light emitting OLED materials eliminates the need to pattern the OLED material for each pixel. In this case, color filters may be used for some subpixels to convert broadband or white light emission into individual colors. For example, red, green, and blue color filters may be used in the mute subpixels of an RGBW device to form red, green, and blue, and the intra-gamut subpixels may emit white without being filtered. In-gamut subpixels are more effective than gamut subpixels because they do not have filters.

2 shows one pixel of the device according to the invention with a stripe pattern of, for example, three gamut subpixels 21a, 21b and 21c, and one intra-mumut subpixel 21d. Shows the cross section of. These subpixels emit light 30a, 30b and 30c with a mute color, and light 30d with an in-mute color. Although the device shown in FIG. 2 appears to be an active matrix with active matrix circuitry 110, other embodiments may be applied to the present invention, which are passive matrices without active matrix circuitry. FIG. 2 also shows a bottom emitting arrangement in which light 30a, 30b, 30c and 30d are extracted in the direction of the substrate. The gamut subpixels 21a, 21b and 21c are formed using a microcavity structure. The microcavity structure is formed using a reflector and a semi-transparent reflector. An organic EL medium is formed between the reflector and the semi-transparent reflector. The layer between the reflector and the semi-transparent reflector creates an optical cavity, which is then adjusted in thickness and refractive index to resonate with the desired wavelength. Examples of microcavity structures are shown in US Pat. Nos. 6,406,801 B1, 5,780,174 A1, and Japanese Patent 11288736. Preferred materials for highly reflective reflectors include Ag, Al, Au or alloys composed of one or more of these materials. Semi-transparent reflectors are partially reflective and partially transparent. Preferred materials for the semi-transparent reflector include Ag, Au or alloys composed of one or both of these materials. These materials have a thickness selected to be semi-transparent, ie partially transparent and partially reflective. This thickness may for example be in the range of 5 nm to 50 nm, more preferably 15 nm to 30 nm. When using a conductive material to form a reflector or semi-transparent reflector, the reflector, semi-transparent reflector or both can also function as an electrode (anode or cathode) for the organic EL medium. Other semi-transparent reflector structures consisting of a quarter wave stack (QWS) of alternating transparent and alternating high and low indices of refraction are also known and are seen by those skilled in the art. It can be applied to the invention. As shown, in the bottom emitting arrangement where light is visible through the substrate, the semi-transparent reflector is located between the organic EL layers, and the substrate and the reflector are located above the substrate, the semi-transparent reflector and the organic EL layer. Alternatively, in a top emitting arrangement (ie light is visible in the opposite direction of the substrate), the reflector is located between the organic EL layers, and the substrate and the semi-transparent reflector are located above the substrate, the reflector and the organic EL layer.

The active matrix circuit 110 is formed on the substrate 100. The active matrix circuit 110 includes a first thin film transistor (TFT) including a semiconductor active layer 111, a gate dielectric 112, a gate conductor 113, a first insulating layer 114, and a second insulating layer 117. It includes. The active matrix circuit 110 further includes one signal line 116 carrying a light emission signal and one power line 115 powering a transistor. Methods of manufacturing TFT circuits are well known in the art. Although only a single transistor, signal line and power line are shown for each subpixel, typically each subpixel is also a second transistor as well as a capacitor (not shown) and an additional selection line (not shown). (Not shown) as well. It will be appreciated that many types of circuits having different numbers and arrangements of circuit elements are known in the art and a wide variety of these circuits can be used in the present invention. Examples of active matrix arrangements include US Pat. Nos. 5,550,066, 6,281,634 and 6,501,466. Although the illustrated TFT has been processed to have a thin film semiconductor active layer 111, it will be understood that the substrate can actually perform this function using a semiconductor substrate. Although a top gate structure is shown in which the gate conductor 113 and the gate dielectric 112 are above the semiconductor active layer 111, the organic EL device can be driven using a TFT having a reverse structure known as a lower gate. Also known in the art.

Above the matrix circuit, semi-transparent reflectors 120a, 120b and 120c are formed in the gamut subpixels 21a, 21b and 21c, respectively. These semi-transparent reflectors 120a, 120b, and 120c may also be formed of reflective metals, such as Ag, Au, Al, and alloys thereof, which may also be thinned to be translucent. Although not necessarily, it is possible that the semi-transparent reflector also acts as one of the electrodes for the organic EL medium.

The intra-gamut subpixel 21d does not have a semi-transparent reflector, but instead has only a transparent electrode 130. Transparent electrode 130 is typically a metal oxide, such as indium-tin oxide (ITO), zinc-tin oxide (ZTO), tin-oxide (SnOx), indium oxide (InOx), molybdenum oxide (MoOx) , Metal oxides including but not limited to tellurium oxide (TeOx), antimony oxide (SbOx) and zinc oxide (ZnOx). The transparent electrode 130 is also electrically connected down to the active matrix element directly or using an intermediate conductor as shown. By using transparent electrodes without semi-transparent reflectors, intra-gamut subpixels are created that do not have a microcavity structure.

In the case of the gamut subpixel 21a, a transparent cavity-spacer layer 140a is formed above the semi-transparent reflector 120a. The transparent cavity-spacer layer 140a is a metal oxide, such as indium-tin oxide (ITO), zinc-tin oxide (ZTO), tin-oxide (SnOx), indium oxide (InOx), molybdenum oxide (MoOx). ), Tellurium oxide (TeOx), antimony oxide (SbOx) and zinc oxide (ZnOx), but is composed of a metal oxide, but not limited to. If the transparent cavity-spacer layer 140a also serves as an electrode for the organic EL medium 210, the transparent cavity-spacer layer 140a must be electrically connected to the active matrix element. This can be done directly, or if the semi-transparent reflector 120a is a conductive material such as Ag, Al, Au, or an alloy thereof, through the semi-transparent reflector 120a as shown, or using another intermediate conductor. Can be. If the transparent cavity-spacer layer 140a is not conductive, the semi-transparent reflector 120a can act as an electrode for the organic EL medium 210 and will therefore be connected downward to the active matrix circuit 110. Alternatively, the transparent electrode 130, the transparent cavity-spacer layer 140a and the semi-transparent reflector 120a may be formed of three (or more) different layers, in which case the transparent electrode may be combined with an active matrix circuit. In electrical contact, a cavity-spacer layer may be present between the transparent electrode and the semi-transparent reflector. The thickness and refractive index of the transparent cavity-spacer layer 140a are determined by the thickness of the organic EL medium 210 in order to tune the cavity to be resonant at a wavelength preferred for the color of the subpixel 21a, for example red. Optimized in relation to and the refractive index. The tuning of the thickness and refractive index to achieve the desired microcavity luminescence is well known in the art.

The gamut subpixel 21b is similarly constructed using the cavity-spacer layer 140b above the semi-transparent reflector 120b. In this case, in order to tune the cavity so that it can resonate at a wavelength desired for the color of the light for the subpixel 21b, for example green, the thickness and refractive index of the cavity-spatter layer 140b are determined by the organic EL medium 210. Is optimized in relation to the thickness and the index of refraction.

The gamut subpixel 21c is shown herein without having a cavity-spacer layer. In this case, only the thickness and refractive index of the organic EL medium 210 are optimized in order to tune the cavity so that it can resonate at a wavelength suitable for the color of the light for the subpixel 21c, for example, blue. As shown, if the organic EL medium 210 is common to all subpixels, the organic EL medium 210 is optimized only for the gamut subpixels, and the other gamut subpixels utilize each cavity-spacer layer. Are tuned separately. This arrangement minimizes the number of different cavity-spacer layers that need to be deposited and patterned. However, in other embodiments, all the gamut subpixels may include a cavity-spacer layer that is optimized separately for each to be tuned to the desired color. In order to allow the organic EL medium 210 to be deposited unpatterned for each subpixel, it is preferable to use the above-mentioned cavity-spacer layer. However, in other embodiments, one or more organic layers of the organic EL medium can be patterned to tune each microcavity of the gamut subpixels and the thickness or refractive index can be adjusted separately. For this arrangement, the cavity-spacer layer can be used or removed. However, this requires accurate patterning of one or more organic layers.

As disclosed above, to minimize the number of deposition and patterning steps, one of the mute subpixels may not have a cavity-spacer layer. Another preferred method of reducing the number of deposition and patterning steps is the transparency of one of the cavity-spacer layers, for example cavity-spacer layer 140b and the non-gamut subpixel, using the same material, thickness and refractive index. The electrode, for example, the transparent electrode 130, is formed.

It is desirable to use an inter-pixel dielectric layer 160 as disclosed in US Pat. No. 6,246,179 to cover the edges of the transparent electrode to prevent shorts or strong electric fields in this region. If the cavity-spacer is conductive or forms part of the electrode, the inter-pixel dielectric layer 160 also covers the cavity-spacer, as shown. The use of inter-pixel dielectric layer 160 is preferred, but not necessary for successful implementation of the invention.

Each subpixel further comprises an organic layer forming an organic EL medium 210. There are various arrays of organic EL medium 210 layers in which the present invention may be successfully practiced. Examples of organic EL medium layers that emit broadband or white light are described, for example, in co-assigned European Patent No. 1 187 235, US Patent Publication No. 20020025419 (Co-assigned), European Patent No. 1 182 244, US Patent 5,683,823 (co-transferred), 5,503,910, 5,405,709 (co-transferred) and 5,283,182. As shown in commonly assigned European Patent Publication No. 1187235Z2, a white luminescent organic EL medium can be achieved by including the following layers: a hole injection layer 211, disposed above the hole injection layer and having a yellow spectrum A hole transport layer 212 doped with a rubrene compound to emit light in the region, a light emitting layer 213 disposed above the hole transport layer 212 and doped with a blue light-emitting compound, and the photoluminescence An electron transport layer 214 disposed over the layer 213. Other embodiments in which one or more other organic EL medium materials are used for different subpixels can also be applied to the present invention.

On the organic EL medium 210, a reflector 220 is formed. The reflector 220 may be formed of a material such as Al, Ag, Au, or an alloy thereof. The reflector 220 can also serve as the second electrode for the organic EL medium 210.

Although a transparent cavity-spacer is shown here between the semi-transparent reflector and the organic EL medium, in other embodiments a cavity step spacer can be formed between the organic EL medium and the reflector.

In other embodiments where one or more layers of organic EL medium 210 are not common to all subpixels but are individually patterned for each subpixel, the cavity-spacer layer is removed and each gamut subpixel is removed. The microcavity for the mute subpixels can be tuned by tuning the thickness, refractive index or both of the one or more layers forming the organic EL medium 210 separately. In this case, if the organic EL medium 210 is designed to emit broadband light, one of the organic EL medium 210 layers for in-gamut subpixels and one or more gamut subpixels to minimize the number of deposition steps. It is preferred that at least one is the same thickness.

3 shows a cross section of a further embodiment of the invention, which is top emission, ie light 30a, 30b, 30c and 30d are extracted in a direction away from the substrate. In order to realize this top emission arrangement, the reflectors 150a, 150b, 150c and 150d are disposed between the organic EL medium 210 and the substrate 100. These reflectors 150a, 150b, 150c and 150d may be formed of a material such as Ag, Au, Al or an alloy thereof. These reflectors 150a, 150b, 150c and 150d can also serve as electrodes for the organic EL medium 210 as shown, in which case it must be connected downward to the active matrix circuit. In this embodiment, the semi-transparent reflector 230 must be formed above the organic EL medium 210 for the gamut subpixels 21a, 21b and 21c. However, the semi-transparent reflector 230 must be patterned such that it is not present in the intra-gamut subpixel 21d. The transparent electrode 240 must be used above the intra-gamut subpixel 21d. To reduce the need for patterning, as shown, a transparent electrode may also be present over other subpixels, but is not necessary. The transparent electrode 240 includes indium tin oxide (ITO), zinc-tin oxide (ZTO), tin oxide (SnOx), indium oxide (InOx), molybdenum oxide (MoOx), tellurium oxide (TeOx), It consists of a metal oxide, including but not limited to antimony oxide (SbOx) and zinc oxide (ZnOx).

In FIG. 3, reflectors 150a, 150b, 150c and 150d form one electrode for organic EL medium 210, while in other embodiments, separate electrodes are disposed above and reflector of the reflector. It can be formed below the EL medium 210, which then becomes part of the microcavity cavity for the gamut subpixels 21a, 21b and 21c. This electrode is made of indium tin oxide (ITO), zinc-tin oxide (ZTO), tin-oxide (SnOx), indium oxide (InOx), molybdenum oxide (MoOx), tellurium oxide (TeOx), antimony oxide ( SbOx) and zinc oxide (ZnOx), but are not limited to metal oxides.

As shown in FIG. 3, the transparent electrode 240 is located above the semi-transparent reflector 230, but in other embodiments it is located between the semi-transparent reflector 230 and the organic EL medium 210. In this case, the transparent electrode 240 forms one of the electrodes for the organic EL medium 210 for every subpixel, which becomes part of the microcavity cavity.

The disclosed embodiment illustrates one example where the efficiency and lifetime of all the gamut subpixels are improved using the microcavity while maintaining the wideband or white light emitting capability from the in-gamut subpixels. However, other embodiments are possible in which only a portion of the mute subpixels are improved using a microcavity structure. That is, some of the mute subpixels are not constructed to form microcavities. An example of such an arrangement is shown in FIG. 4, which is two microcavity gamut subpixels 22b and 22c, one non-microcavity gamut subpixel 22a and an intra-gamut subpixel ( 22d). In this case, the non-microcavity gamut subpixel 22a is formed using the reflector 220 and the transparent electrode 130a. The transparent electrode may be of the same material and thickness as used for the transparent electrode 130d of the intra-gamut subpixel 22d. When the organic EL medium 210 used emits white or broadband light, the color filter 301 can be used to obtain the desired gamut color for these subpixels. The use of color filters to convert broadband emission into narrowband emission of a particular color is known in the art. As long as at least one of the mute subpixels is built into the microcavity, some improvement in lifetime and efficiency will be realized according to the present invention.

While the invention has been described in detail with specific reference to certain preferred embodiments, it will be understood that changes and modifications can be made within the spirit and scope of the invention.

Claims (17)

(a) an array of luminescent pixels, wherein each pixel comprises organic layers comprising one or more luminescent layers generating light and subpixels having spaced apart electrodes, here producing a color defining a color gamut Three or more gamut subpixels and one or more subpixels that generate light within the color gamut generated by the gamut subpixels); (b) wherein at least one of the gamut subpixels comprises a reflector and a semi-transparent reflector, the function of forming a microcavity, The gamut subpixel having the microcavity structure further comprises a transparent cavity-spacer layer, wherein the thickness of the transparent cavity-spacer layer, the thickness of the transparent cavity-spacer layer, to tune the microcavity to a desired color. The refractive index or both are adjusted separately for each other color gamut subpixel, along with the refractive index and thickness of the organic layer for each gamut subpixel. The method of claim 1, And the reflector also serves as an electrode for one or more subpixels. The method of claim 1, Wherein the semi-transparent reflector also acts as an electrode for one or more subpixels. The method of claim 1, And wherein the color produced by the mute subpixels is red, green and blue and the color produced by the intra-gamut subpixel is white. The method of claim 1, And the organic layers emit broadband light and are common to all subpixels of all pixels. The method of claim 5, At least one of said mute subpixels further comprises a color filter element. The method of claim 1, OLED device wherein the device is a passive matrix device. The method of claim 1, OLED device wherein the device is an active matrix device. delete The method of claim 1, And the transparent cavity-spacer layer of one of the mute subpixels is formed of the same material and thickness as the transparent electrode of one or more of the sub-gamut subpixels. The method of claim 1, All but one of the gamut subpixels having a microcavity structure further comprises a transparent cavity-spacer layer, wherein the thickness of the transparent cavity-spacer layer, in order to tune the microcavity to a desired color, And the refractive index or both of the transparent cavity-spacer layer are adjusted separately for each other color gamut subpixel, together with the refractive index and thickness of the organic layer for each gamut subpixel. The method of claim 11, Wherein the transparent cavity-spacer layer of one of the mute subpixels is formed of the same material and thickness as the transparent electrode of one or more of the sub-gamut subpixels. The method of claim 1, At least one of the organic layers is patterned separately for at least one subpixel. The method of claim 13, At least one of the organic layers is patterned separately for each gamut subpixel. The method of claim 13, Wherein the organic layers emit broadband light and all layers of the organic layers are the same for one or more of the mute subpixels and for one or more of the in-mute subpixels. The method of claim 1, And the device is bottom emitting. The method of claim 1, OLED device wherein the device is top emitting.

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